This invention relates to fuel injection control of a diesel engine for a vehicle.
JP2000-54901A published by the Japanese Patent Office in 2000 discloses a fuel injection controller of a diesel engine which adjusts the fuel injection timing of a fuel according to the magnitude of a difference between a target intake air amount and a real intake air amount, when the difference arises.
In a diesel engine provided with an exhaust gas recirculation (EGR) mechanism, recirculated exhaust gas becomes a part of the air aspirated by the engine, so the delay of recirculated exhaust gas poses a problem. As the above-mentioned conventional fuel injection takes only the delay of the fresh air into account, it is inapplicable to a diesel engine provided with an EGR device.
When the intake air amount of an engine varies owing to a rapid change in a engine load etc., the exhaust gas recirculation amount actually aspirated by the engine accompanies with a time lag to the target exhaust gas recirculation amount calculated by a controller.
As the recirculated exhaust gas forms part of the intake air, the real excess air ratio of the engine is delayed relative to a target excess air ratio calculated by the controller. If the fuel injection timing is adjusted by calculating the difference between the target excess air ratio and a real excess air ratio without correcting for this delay, the timing that a fuel injection device injects fuel shifts from an optimal fuel injection timing. In this case, the engine generates a noise and a torque shock, which causes discomfort to the driver.
It is therefore an object of this invention to provide a fuel injection controller of a diesel engine for a vehicle which takes the delay of the exhaust gas recirculation into account, and adjusts the fuel injection timing of the fuel accordingly.
To achieve the above object, a fuel injection control device for a diesel engine is provided with a fuel injection mechanism that controls a timing of fuel injection, an exhaust gas recirculation mechanism that recirculates part of exhaust gas into air introduced into a cylinder of the engine, and a turbocharger that pressurizes fresh air introduced into the cylinder of the engine. The fuel injection control device comprises a sensor that detects a running condition of the engine and a programmable controller.
The programmable controller is programmed to set a basic fuel injection timing based on the running condition of the engine, set a target excess air ratio based on the running condition of the engine, correct the basic fuel injection timing according to a delay of a real exhaust gas recirculation amount to a target exhaust gas recirculation amount, and control a fuel injection timing of the fuel injection mechanism according to to the corrected fuel injection timing.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.